Coal screen



July 2, 1929. FIA. KREHBIEL '1 1.719.513

COAL SCREEN Filed Feb. 24, 1925 Patented July 2, 1929.

UNITED STATES FREDERICK A. KREHBIEL, F I-IINSDALE, ILLINOI S.

GOAL SCREEN.

Application filed February 24, 1925. Serial No. 11,588.

accelerated motion of the coal for the pur-' pose of turning the coal during its screening. In the diagrammatic illustrations showing one embodiment of my invention, in which like reference characters indicate like or corresponding parts: v

Figure 1 is a vertical section through a screening apparatus showing my invention. Figure 2, shows a slight modification of the reciprocating screens, and Figure 3 is across section taken on line 33 of Figure 1.

The coal is conveyed and discharged into a dump hopper 10by means of a conveyor or mine car 11 as here shown for illustrative purpose. From the dump hopper 10 the coal is fed by a reciprocating plate feeder 12 to the reciprocating upper screen 13, which is mounted on rollers 13.

The upper screen 13 may be of any desirable width and length and may be provided with any number of screen plates depending upon the design of the plant and number of sizes of coal made.

In the present illustration, three, sizes of coal are prepared, slack or fine coal, the nut or medium size, and the large lump. The screen 13 is provided with a short horizontal slack screen section 13 a slightly inclined nut screen section 13 and a horizontal discharge end section 13 of blank plate, where the large lump coal canbe hand-picked be fore its discharge over the lump chute 18 into the lump car. A narrow trough 13 supported centrally over screen 13 on bars '13 which are rigidly fixed to the upper screen 13, is arranged to convey the refuse into a chute 19 which can be adapted for discharge onto a bin or conveyance of any suitable type. Beneath the upper screen 13 is a lower reciprocating screen 1 1 which is also mounted on rollers 1 1 but which conveys the coal in an opposite direction to that of the upper screen, due to its connecting rod 16 being connected to drive eccentric 17 which is oppositely disposed to the upper screen drive eccentric 17 screen 13. 1

The lower screen 14 is provided with a slack or fine coal screen 1 1 over the middle track.

' The side deflecting plates 14: send the fine, or slack coal which passes through the screen 14?, into a slack hopper lt which is provided with a slidable gate 14 and chute 1-1 to control its loading into the railroad car. The slack coal passing through the screen 13 is deflected over chute 13 for direct discharge into the slack hopper 1 1 through chute 22.

The oversize or nut coal passing over the screen 14 enters the extended horizontal section 14 where the coal can be hand-picked just before it is discharged onto the chute 20 for loading onto the car. 1 Any drive mechanism 17 suitable for imparting a conveying motion-to particles on vhorizontally reciprocating troughs can be employed. 1 have preferably indicated the mechanism shown and described in the patent to Richard S. J acobsen, No. 1,289,791, dated December 31, 1918.

A connect-ing rod 21 driven by an adjustable eccentric mounted on the drive shaft of the mechanism 17 imparts a reciprocating motion to the feeder plate 12 whereby the coal is uniformly fed to the screens. As the mixed or run of mine coal enters upon the screen 13 part of the slack or fine coal is immediately removed by screen 13 and this fine coal is by-passed, as above stated, directly to the slack hopper 14 The coal then passes over the slightly inclined screen 13 which is formed in stepped sections as clearly shown in Fig. 1. The screen plate 13 is provided with perforations large enough to remove the two smallest sizes, namely, slack and nut.

Heretofore these screen plates weremounted horizontally and contiguous with remainder of the trough but I have found that by slightly inclining these screens and stepping them, that the coal will pass over with a gradually or progressively increasing speed or motion which produces the very desirable result of separating the pieces'or particles a further distance apart, and then turning the coal every so often, so as to remove any fine or slack coal which might ride on the larger or lump coal. This process of screening produces the most efiicient method of separation or grading that is possible with reciprocating screens. A further great advantage lies in the provision of the picking space 18 where the lump coal can readily be hand-picked of refuse or slate before discharge onto the lump car.

In the modified screens shown in Fig. 2, the construction and process of operation of the screening is similar to that above described except that in this instance, the nut screen plate 23 of the upper reciprocating trough 24L 'and. the slack screen plate 25 of the lower reciprocating trough 26, are both curved, thus affording a gradually or progressively downwardly inclined screen.

Perhaps it should be noted here, that the provision of the short section of preliminary slack screen 13 and the arrangement of deflecting and by-passing this slack directly onto the hopper 14: has materially advanced the efliciency of screening coal on horizontally reciprocating screens, and it is now apparent that with a portion of the slack already removed, the efficiency of the screen 13 which removes both slack and nut, is increased.

I claim 1. A unit screen mounted for horizontal reciprocation, said unit having a perforated horizontal screen portion, an unperforated horizontal portion, said portions lying in different lateral planes, and an inclined perforated screen section connecting said portions, said unit adapted .during its horizontal reciprocation to convey material to be screened from the perforated horizontal screen portion over the inclined screen section and thence over the unperforated horizontal section.

2. A unit screen as embodied in claim 1 and including said inclinedscreen section with a step within its length.

3. A material screening unit mounted for horizontal reciprocation, said unit having a,

during its horizontal reciprocation to convey material to be screened from the perforated horizontal screen portion over said intermediate screen section and thence over'the unperforated horizontal section, the surface of said intermediate perforated screen section being so formed that succeeding points on the longitudinal center line thereof will be progressively on a lower lateral plane in the direction of the movement of the material thereon, whereby the additional force of gravity may act upon the material as it is conveyed during screening thereof so that the over-size material passing over said surface of said intermediate screen will move with an accelerated motion.

4. A material screening unitmounted for reciprocation, said unit having a perforated horizontally disposed material conveying trough portion, a second horizontally disposed trough portion, said trough portions lying in different lateral planes, and an intermediate perforated trough section connecting said first-named trough portions to produce one continuous trough from one end of said unit to the other end thereof, said unit being adapted during its reciprocation to convey the material from the perforated horizontal screen portion located in the higher level, thence over said intermediate screen section, and thence over said second horizontal. portion located in the lower level of said unit, the surface of said intermediate perforated screen section being so formed that succeeding points on the longitudinal center line thereof will be progressively on a lower lateral plane in the direction of the movement of the material thereon, whereby the additional force of gravity may act upon the material as it is conveyed during screening thereof so that the over-size material passing over said surface of said intermediate screen will move with an accelerated motion.

In witness whereof I affix my signature.

FREDERICK A. KREHBIEL. 

